This invention relates to an output split-type mechanical and hydraulic power transmission.
More particularly, this invention relates to an output split-type mechanical and hydraulic power transmission having a plurality of input-output speed ratio ranges.
In a conventional output split-type mechanical and hydraulic transmission utilizing a single input-output speed ratio range, the required horsepower capacity for a hydraulic pump motor used in the transmission is large. Because of this, conventional power transmissions of this type are severely limited in a practical sense, i.e., the transmission is extremely expensive to manufacture, is large in size, and has a low power efficiency.
To attain the wide variation of speed changes required in automotive vehicles, conventional power transmissions have used a plurality of input-output speed ratio ranges. However, even when output split-type mechanical and hydraulic transmissions have incorporated the use of a plurality of input-output speed ratio ranges, no completely satisfactory results have been achieved and numerous problems have been encountered in meeting the necessary conditions and requirements. It is necessary that an output split-type mechanical and hydraulic transmission not only employ a plurality of input-output speed ratio ranges but also be small in size and low in manufacturing cost, have maximum power efficiency, and allow a high degree of design flexibility to meet the input-output speed ratio ranges requirements.
Accordingly, it is a primary object of this invention to provide a new and improved output split-type mechanical and hydraulic transmission employing a plurality of input-output speed ratio ranges.
It is a further object of this invention to provide a new and improved output split-type mechanical and hydraulic transmission having a high degree of design flexibility for establishing the plurality of input-output speed ratio ranges in accordance with predetermined requirements.
Another object of this invention is to provide a new and improved transmission of the above-described type wherein each input-output speed ratio range is continuous to make possible a continuous variable drive ratio.
Another object of this invention is to provide a new and improved transmission of the above-described type which has clutch and brake means for establishing the plurality of input-output speed ratio ranges that are synchronized on the border of adjoining input-output speed ratio ranges, thus decreasing the size and capacity of the conventional clutch and brake means.
Another object of this invention is to provide a new and improved transmission of the above-described type which minimizes size, weight and manufacturing cost by employing a commonly used differential gear mechanism for establishing the plurality of input-output speed ratio ranges.
Still another object of this invention is to provide a new and improved transmission of the above-described type wherein the components of the differential gear mechanisms have rotational speeds maintained within practical limitations thereof.
A further object of this invention is to provide a new and improved transmission of the above-described type which minimizes a countershaft-type speed-reducing element for decreasing bearing-receiving radial loads.
Finally, it is an object of this invention to provide a highly simplified output split-type mechanical and hydraulic transmission which is small in size, and low in weight and manufacturing cost, while transmitting maximum and continuous drive power.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing objects and in accordance with the purpose of the invention, as embodied and broadly described herein, the output split-type mechanical and hydraulic transmission of this invention comprises: (1) an input shaft; (2) an output shaft; (3) an intermediate shaft; (4) differential gear means for establishing different input-output speed ratios, the differential gear means having at least one component mechanically connected to the input shaft, one component mechanically connected to the intermediate shaft, and one component mechanically connected to the output shaft; (5) clutch means for selectively cooperating with components of the differential gear means, the input shaft, the intermediate shaft, and the output shaft to establish different input-output speed ratio ranges; and (6) first and second hydraulic pump motor means hydraulically connected to each other, at least the first pump motor means having a variable hydraulic capacity and being mechanically and driveably connected to the input shaft for establishing variations in the hydraulic capacity, and at least the second pump motor means being mechanically connected to at least one component of the differential gear means for establishing rotational speeds of the components of the differential gear means during the different input-output speed ratio ranges in relationship to the variations of the hydraulic capacity of at least the first pump motor means.
It is preferred that the output split-type mechanical and hydraulic transmission include a first differential gear mechanism having at least four elements, the first element being connected to the input shaft, the second element being connected to the second pump motor, and the third and fourth elements being selectively engageable with the intermediate shaft by the clutch means, and a second differential gear mechanism having at least three elements, the first element being connected to the input shaft, the second element being connected to the intermediate shaft, and the third element being connected to the output shaft.
It is further preferred that the clutch means of the output split-type mechanical and hydraulic transmission selectively connect and disconnect the intermediate shaft and the second element of the second differential gear mechanism with the output shaft.
Finally it is preferred that the output split-type mechanical and hydraulic transmission have the differential gear mechanisms, and the intermediate and output shafts coaxially arranged with the input shaft, and the hydraulic pump motors including rotational shafts parallel to the input shaft.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and, together with the description, serve to explain the principles of the invention.